从数据库获取派生列 SQL查询 DB2 SystemDate

Question

My table is PRODUCTINFO :

Column name : product_name | launch_date
Sample Date : product1       2017-01-20

I need a SQL query to decide if the product is newly launched or not.

Business rule :

if (launch_date - currentdate < 0 && currentdate - launch_date < 90) 
    newly_launched = 'YES'
else 
    newly_launched = 'NO'

where currentdate is today's date.

SQL query I am witting is like :

SELECT launch_date, X as newly_launched 
FROM PRODUCTINFO 
WHERE product_name = 'product1'

I am not able to figure out correct replacement of 'X' in my query for desired result.

Problem I am facing is using currentdate and if else block in my query

Please help.

One way to get currentdate in DB2 using following query :

SELECT VARCHAR_FORMAT(CURRENT TIMESTAMP, 'YYYYMMDD')
FROM SYSIBM.SYSDUMMY1

Still not sure how to use this with my if else scenario.

Answer here don't solve my problem as this scenario is if-else based.

Answer 1

use TIMESTAMPDIFF with 16 as first parameter for count number days between 2 timestamps, for more detail look here

try this

select launch_date, 
case when TIMESTAMPDIFF( 16, cast(cast(launch_date as timestamp) - current timestamp as char(22))) >0 and 
 TIMESTAMPDIFF( 16, cast(cast(launch_date as timestamp) - current timestamp as char(22))) <90 then 'YES' else 'NO' end newly 
from PRODUCTINFO
WHERE product_name = 'product1'

Answer 2

simply use datediff function in a case syntax, I hope it could help!

SELECT launch_date,
        case
            when DATEDIFF(day,launch_date,getdate()) BETWEEN 0 AND 90 then 'YES'
            else 'NO'
            end AS newly_launched
FROM PRODUCTINFO
WHERE product_name = 'product1'

in case you want to do it for all your records:

SELECT launch_date,
        case
            when DATEDIFF(day,launch_date,getdate()) BETWEEN 0 AND 90 then 'YES'
            else 'NO'
            end AS newly_launched
FROM PRODUCTINFO